Ink jet pens typically require an ink filter to be placed between the ink reservoir and the nozzle, preferably close to the nozzle, to filter out particles and impurities in the ink. These particles often arise either from poor processing of the ink prior to insertion into the pen, or from unsanitary conditions during the assembly of the pen. If a particulate of a dimension larger than an ink flow passage were to get stuck in the passage, it could slow or prevent the flow of ink to the nozzle. Thus, an effective filter prevents an early failure of the ink jet pen due to such a particulate, and prolongs its life by reducing long-term contamination.
Filters for ink jet pens have taken on many forms. For example, U.S. Pat. No. 6,254,229 to Bohorquez et al. discloses a filter member having a plurality of holes coupled to a flat microscreen filter. U.S. Pat. No. 6,234,623 to Drake discloses first and second filter arrays patterned onto layers. U.S. Pat. No. 5,537,136 to Brandon et al. discloses a filter cap including a mesh material formed into a dome-shaped configuration. U.S. Pat. No. 6,152,560 to Hollands discloses a filter element made of a sheet-like material having a curved shape. U.S. Pat. No. 5,949,458 discloses a fibrous body to act as a filter. U.S. Pat. No. 5,546,109 to Nakano discloses a flat filter member that is interposed between two thin films permeable to air.
However, as pen performance increases, a higher ink flow rate is required, thus requiring a higher effective filtration surface area of the filter media. Typically, the filters in the prior art have small effective filtration surface areas. There is thus a need for ink jet filters having a larger effective filtration surface area and, hence, a higher filtration rate.